(Solved): Customers arrive at a movie theater at the advertised movie time only to find that they have to sit ...

Customers arrive at a movie theater at the advertised movie time only to find that they have to sit through several previews and prepreview ads before the movie startsi lany complain that the time devoted to previews is too long. A preliminary sample conducted by the Wall street Journal showed that the standard deviation of the armount of time devoted to previews was 4 minutes. Use that as a planning value for the standard deviation in answering the following questions. Round your answer to next whole number. A. If we want to estimate the population mean time for previews at novie theaters with a maroin of error of 75 seconds, what sample alte thould be used Assume $95\%$ conflidence: b. If we want to eatimate the nopulation mean time for previews at movie theaters with a margin of error of 1 minute, what sample size should be ubed? Assume $95\%$ confidence,